Most railway locomotives are operated by the manipulation by hand of three controls: a throttle control, a brake control and a forward/reverse direction control. Generally, these controls comprise handles movable between a plurality of operational positions. These controls are often, if not always, contained within an integrated controller unit. U.S. Pat. Nos. 3,842,653 (granted 22 Oct., 1974 to Blonn, Sr.) and 5,542,891 (granted 6 Aug., 1996 to Kettle, Jr.) show two similar types of integrated controller units used in most locomotives in North America.
In these common types of locomotive control systems the throttle and brake handles cannot be removed from the controller unit. However, the forward/reverse controller is a separate key-like handle (shown in FIG. 13 of the Blonn Sr. patent, and in FIG. 10 of the Kettle, Jr. patent) which must be inserted into a chamber or "keyhole" in the controller unit before the locomotive can be operated. The "key" typically has a generally circular profile, with a square ridge running the length of it. Similarly, the chamber has a generally circular cross section, but with a generally square or U-shaped groove running its length.
The handle, once inserted, can be moved between three positions: forward, reverse and neutral. The handle can only be inserted and removed when the controller is in the neutral position (ie. when the locomotive is at rest).
This forward/reverse control handle is typically removed from the controller unit when the train is not moving, especially when the train is "parked", thereby preventing the mistaken or unauthorized operation of the locomotive. The handle must be re-inserted before the locomotive can be operated. A significant problem exists with this system in that these handles are occasionally lost, misplaced and/or stolen, and may be used by unauthorized personnel, disgruntled employees and even joy riders and vagrants to move trains. This is not a trivial concern, since a significant number of such handles go missing every year.
A locking device is accordingly desired which can be lockedly inserted into the chamber normally occupied by the controller handle thereby preventing the insertion of an unauthorized handle. This disables the control unit and prevents unauthorized operation of the locomotive. Preferably, such a device would be small and lightweight, easily carried by those members of a train crew authorized to disable the locomotive.